1. Field of the Invention
This invention relates to a process for the preparation of indoles by reacting aniline or a derivative thereof with a 1,2-glycol in the presence of an improved catalyst.
2. Description of the Prior Art
In the past, the present inventors discovered that indoles can be directly prepared in a single step through the reaction of aniline or a derivative thereof with a 1,2-glycol and that certain catalysts are useful in promoting this reaction. Several processes based on these discoveries have already been disclosed. Moreover, another process for the preparation of indoles by contacting aniline or a derivative thereof with ethylene glycol in the vapor phase is disclosed in Japanese Patent Laid-Open No. 36451/'81. This process is characterized in that the vapor phase reaction is carried out in the presence of a catalyst which is commonly used for the dehydrogenation of alcohols.
The present inventors have made further investigation and examination of such catalysts and have now found that a specific type of silver catalyst serves as a very excellent catalyst for the above-described reaction.